Vacuum furnace batch feeding method and apparatus



Feb. 7, 1956 c. E. NEWCOMB ETAL 2,733,912

VACUUM FURNACE BATCH FEEDING METHOD AND APPARATUS Filed Aug. 30, 1954 2Sheets-Sheet 1 w/iumwauxhwmm ATTORNEYS.

Feb. 7, 1956 c, EQNEWCOMB ET AL 2,733,912

VACUUM FURNACE BATCH FEEDING METHOD AND APPARATUS Filed Aug. 30, 1954 2Sheets-Sheet 2 INVENTORS. CHARL 5 E. Nswcona.

JOHN A. Peers/e. y PA 01. E. Dnesn MMJMM ATTORNEY-5.

United States PatentO .VACUUM FURNACE BATCH FEEDING METHOD AND APPARATUSCharles E. Newcomb, Industry, Pa., John R. Porter, Chester, W. Va., andPaul F. Darby, Beaver, Pa., assignors to' Rem-Cm Titanium, Inc.,Midland, Pa., a corporation of Pennsylvania Application August 30, 1954,Serial No. 452,965

8 Claims. (Cl. 266-27) This invention relates to means and methods forfeeding charges of highly reactive metals, such as titanium sponge, andtheir alloying ingredients to a vacuum-tight ice * precise proportionateratio of ingredients desired as the melting furnace in such manner as toproduce a homo- 1 geneous ingot having the desired overall chemicalanaly- In the melting of titanium base alloys and alloys of othersimilar highly reactive metals, the chargeof material to be meltedcommonly consists of a mixture of the various desired ingredients ingranular, comminuted or pulverulent form. Due to wide differences in thegravimetric densities of these various materials, gravitationalseparation of the samewill occur if an attempt is made to mix the entirecharge in a single hopper. This gravitational separation will, ofcourse, preclude homogeneous feed to the furnace from that singlehopper, and such homogcneousfeed has been found necessary for theproduction of a structurallyhomogeneous ingot; the reason being that inthe melting of such highly reactive metals, the ingots are built up bitby bitjas the charge is fed gradually into the 'furnace' with only arelatively small portion ofthat charge being in the molten state at anyone time and therefore, unlessthat particular portion of the chargeiwhich is' molten is homogeneous, a non-homogeneous ingot willre'sult.

In'or dert'o provide suchari'ultim'ate homogeneous ingot structure'various homogeneous feed apparatus and methods are presently in usewhich call for individualiy but simultaneously feeding each particularingredient of the charge from a'separate hopper while cont'rolli'rigtherates of feed of these various ingredients in accordance withultimateproportionaterequirements of the alloy melt. In such systemsmaintenance of the proper proportionate feed is a matter of constantconcern to the-operators 'of the furnace: Moreover, such systemsgenerally employ a plurality of rotating screw feed means or the likejeach extending into the furnace through a wall thereof,and since thesefurnaces must be maintained vacuum-tight, vacuum-tight sealing meansmust be provided at the'e'ntry points'of these feed screws. Maintenancein operation offsuch' sealing means is quite dilficult'] p AOurinvention herein eliminates the necessity of main raining a closelycontrolled proportionate feed, and provides a method and apparatus forfeeding such charges to 'a-vacuum-tight furnace from a single hopper;Moreover, the invention largely eliminates the necessity of amultiplicity of difiicult tomaintain vacuum-tight seals forrotaryfeed'screws and the like, andrequires but a single'and simplevacuum-tight seal for a pulsating shaft. According to'the' invention "anincremental feeder is provided whichpermi'ts the use of blended chargesof such small size that mechanical separation 'of the variousingredients thereof due to igravity is unimportant. in accordance withtheincremental feed method'of the invention, the total charge necessaryfor the production of any ;given' size=ingot is made up --byindividually; blending a plurality of small charge batches, each havingthe overall chemical analysis for the ingot to be produced, and thenfeeding said batches successively to the furnace without regard forhomogeneous feed of each individual batch. The precise size of thesebatches will, of course, depend upon the particular operating conditionsinvolved, such as the size of the furnace, and the size of ingot to beproduced, but inany event each batch will be sized so as to be smallerthan the portion of the charge which is in the molten state at any onetime in the furnace. If, for example, itwere desired to produce a 4000pound ingot containing 4% aluminum, 4% manganese and the balancetitanium, the incremental feed apparatus and method of this inventionwould call for forty individual one-hundred pound charge batches to bemade up, each precisely weighed and blended according to the desiredration of 92% Ti4% A14% Mn. and then fed successively into the furnace.Since the densities of these particular alloying ingredients varywidely, i. e., specific gravitiesTi, 4.5; A1, 2.7; Mn, 7.2,gravitational separation would probably occur in each of the forty smallcharges. Thus, as each of these charges is fed into the furnace the feedmay not be homogeneous, that is, the composition of each hundred poundcharge mayvary from pound to pound. Nevertheless, substantial homogeneityof the ingot produced is assured, since the overall compositionof each 100 pounds is precisely correct, and since'the amount of metalin the molten state in the furnace crucible at any one time is bypredetermined 'design substantially greater than 100 pounds, eachincremental 100 pound batch will be further blended into a homogeneousmixture while within this molten bath of the furnace. I

The incremental feed apparatus according to. the invention comprisesupper and lower interconnected feed hoppers with a charge restrainingbutterfly-type valve and a vacuum closur'e'ball-type valve disposed inthat order in the line connecting the upper hopper with the lowerhopper. Disposed beneath the lower hopper is a vacuum-tight enclosurewhich is in open communication both with said lower hopper and with thefurnace, and in which there is positioned a reciprocating feed troughwhich is designed to receive the batch of charge from the lower hopperand deliver the same to the furnace itself. Suitable sealing means areprovided tomaintain the aforedescribed system gas-tight. Thereciprocating feed'trough is activated by a pulsating magnet assemblywhich is positioned exteriorly'of the aforementioned vac uum-tightsystem, its only connection therewith being a pulsating drive shaftwhich extends through a wall of the enclosure so asto be operativelyconnected. to the feed trough. The upper hopper is provided with both aninert gas inlet line and a vacuum line, the latter running to a suitablevacuum pump, with each of said, lines being provided with vacuum closurevalves, While the furnace itself is of course suitably connected tovacuum pumppers are initially closed and the furnace, together withconnecting feed trough enclosure and lower hopper, are pumped down tothe desired vacuum. The first preweighed incremental batch of charge ofa size and character as described above, is then delivered to the upperhopper. This upper hopper is then sealed and pumped down to the desiredvacuum, generally corresponding to the pressure ofthefurnace. The vacuumclosure ball valve and charge restraining butterfly valve are thenopened 'in that order, thereby permitting the batch of charge in theupper hopper to' fall by gravity to the lower hopper from whence it isfed to the furnace by the feed trough. The rate of reciprocation of thetrough and hence the ratefof feed to the furnace can, if desired,

be varied by providing a suitable rheostat control unit in theactivating magnet assembly. As soon as theupper hopper is empty thebutterflyfand vacuum closure valves in the line connecting the twohoppers are then closed, and the upper hopper is fiooded'with an inertgas, such as argon, until approximately atmospheric pressure is attainedtherein. The next incremental batch is then delivered to the upperhopper and as soon as the first batch has emptied fr om the lowerhopper, the above described procedure is" repeated over and over untilthe entire charge has been fed to the furnace.

It will be observed that only the drive shaft of the pulsating magnetassembly passes through a wall of the aforedescribed vacuum-tight feedsystem'and since this shaft is limited to pulsating or reciprocatingmovement, it may be readily sealed in gas-tight fashion, according toconventional, well known means. Therefore the apparatus of the inventionprovides a system wherein the opportunity for, and chance of vacuumleaks is held to a minimum. Such a system moreover provides a relativelysimple apparatus, which is subject to a minimum of mechanical failures.The present invention, moreover, provides better control of ingothomogeneity than has heretofore been possible undercomple x existingmethods and moreover reduces the safety hazards involved, since theamount of highly active metals such as titanium sponge contained in thehopper at any given time is substantially reduced. The invention findsutility in all type furnaces for melting highly reactive metals, whereinthe chargeis fed in granular or particle form to the furnace, and, evenin the consumable electrode arc-melting type of furnace, which does notemploy such a type of charge feed, theinvention can be employed to addlower melting point elements which are desired in the final ingot, butmight prematurely melt out of the consumable electrode'if supplied inthat fashion.

Other and more specific objects, features and advantages of theinvention will appear from the detailed description given below, takenin connection with the accompanying drawings which form a part of thisspecification and illustrate by way of example the present preferredembodiment of the invention.

In the drawings:

Figure 1 is a vertical elevational view of the entire incremental feedapparatus of the invention. A

Figure 2 is an enlarged, fragmentary cross-sectional view of the upperportion ofthe apparatus of Figure 1, showing the butterfly and vacuumclosure valves in the line connecting the upper and lower hoppers.

Figure 3 is an enlarged, fragmentary cross-sectional view of the lowerportion of the apparatus of Figure 1, showing the feed trough with itsactivating magnet assembly. 1

Referring now in more detail to the drawings and partlcularly to Figure1 the incremental feed apparatus of the invention, as shown, comprisesan upper feed hopper having .a pivoted closure lid 11, which is providedwith a resilient annular gasket 12 designed to render the hopper 10vacuum-tight when the lid is pivoted to the closed position shown andpressure is applied thereto. heading into this upper feed hopper is aninert gas entry line 13 having a vacuum closure valve 14'of suitableknown type, and a vacuum line 15 having a suitable vacuum closure valve16 of known construction. Positioned beneath the upper feed hopper andconnected therewith by means of a conduit or feed line 17 is a lowerhopper 18, the lower endof which is open and continuous communicationthrough a vacuum-tight enclosure 19 with a furnace 20, which latter maybe of any conventional design for producing ingots of highly reactivematerials such as titanium sponge. It shouldbe of course understood thatthe furnace 20 is provided with suitable connections leading to vacuumpump-down'means ,2,7as,912 p t (not shown) adapted to maintain thefurnace at the desired low operating pressure. I

Referring now m'rigure 2 it will be seen that in the line 17 whichinterconnects hoppers 10 and 18 there is positioned, immediately beneaththe upper hopper, a charge restraining butterfly-type valve 21 having anoperating lever 22. Beneath this-charge restraining valve a ball-typevacuum closure valve 23 is located in the line 17. This valve is ofstandard construction and comprises a ball seat 24 having a gas-tight,sliding fit with a ball 25. The ball 25 is providedwith acentralpassageway 26 and is adapted to be rotated by anoperating lever 2'7 fromthe closed position, as shown'in Fig. 2, to its open position whereinpassageway 26 is aligned with the hopper interconnecting conduit 17; Thehopper 18 has an open lower end 23 which extends, into enclosure 19, thehopper and enclosure being welded together as at 28a. This enclosurelt9, as mentioned above, is in open communication at one end 29 with theinterior of furnace 20 and is provided at its other end with avacuum-tight closure plate 30. Suitable resilient annular gaskets 31,31', 32,

' and 33 are provided at the juncture points of the feed line 17 andenclosure 19 so as to effectively seal the above described system invacuum-tight fashion. Positioned beneath the open end 28 of the lowerfeed hopper 18 is a reciprocating or vibrating conveyor feed trough 34which is designed to receive material from the hopper and deliver thesame to the furnace. Vibratory conveyors employing such a trough arewell'known and comprise in conjunction therewith a power drivenvibratory mechanism connected to the trough at one end for deliveringlongitudinal vibrations to it, whereby material deposited on the troughat one end is caused to travel continuously thereover for discharge atthe other end. Herein the necessary vibratingor reciprocating movementis delivered to the trough 34 by a pulsating magnet asembly 35 having apulsating shaft 36 which is connected at 37 to one end of the feedtrough. As is customary in such conveyor mechanisms, the feed trough 34is resiliently mounted so as to have an nace.

upward component of motion as it moves forward toward the furnace and adownward component of motion as it returns rearwardly away from thefurnace in order to therebypropel the charge material forwardly to thefur- As shown, this resilient mounting comprises a pair of elongated,rectilinear leaf springs 38 and 38', but it should be understood thatany suitable resilient mounting could be employed. These mountingsprings 38 and 38 not only permit the desired vibratory or reciprocatingmovement of the feed trough delivered to the latter by the primermovermagnet assembly 35, but also the inherent regenerative force ofthose springs serves to aid the prime movers efforts.

The prime mover magnet assembly is of thepulsating type of well knowndesign and comprises a winding 39 which is suitably connected to asource of energizing, alternating current, as indicated at 40, a core 41which is attached to the shaft 36 via connector 42. Cylindrical guidemeans 43 holds the shaft 37 in proper alignment for passing through avacuum-tight seal 44 which is provided in the closure plate 30 of thefeed trough enclosure 19. This vacuum-tight seal 44 includes asemi-spherical resilient O-ring 45 which embraces the shaft 36 ingastight sealing relationship. Analternative means of providing thisseal is by means of a section of rubber tubing surrounding and extendingbetween shaft 36 and housing 44 andclamped at its opposite ends to theseelements respectively. The pulsatingmagnet assembly is operativelypositioned exteriorly of the aforedescribed vacuum-tight charge feedingsystem, being mounted on a rigid frame 45 which is attached by suitablemeans 46 to the closure plate 30 of enclosure 19. Only the pulsatingshaft 36 extends, as described above'in gas-tight relationship throughthe closure plate 30 of the enclosure 19. Therefore the magnet assemblyneed not be sealed'fr'om the atmosphere and hence itssupporting frame 45may be of the open hopper is then opened and the first incremental'batchof charge introduced thereinto. Lid 11 is then closed and, with valve 14of the inert gas line in the closed position, valve 16 of the vacuumline is moved to its open position and the hopper 10 pumped down to thedesired vacuum pressure as indicated on a suitable gauge 50, whichpressure will ordinarily correspond to the operating pressure of thefurnace. During this pump-down of hopper 10 the force of atmosphericpressure on the upper surface of the lid 11 will cause the sealinggasket 12 to be compressed thereby effectively sealing this upper hopperin gas-tight fashion from the ingress of harmful atmospheric gases. Whenthe desired vacuum has been attained in hopper 10 the vacuum closureball valve 23 is first moved to its open position with passageway 26aligned with the hopper interconnecting line 17. As shown, at this pointin the process, since the charge restraining butterfly valve 21 is stillclosed the titanium sponge or other material 51 contained in hopper 10will be prevented by said butterfly valve from contacting the ballclosure valve. This is most important since such charge material isgenerally highly abrasive, and if the same were permitted to be incontact with the valve seat 24 of the ball valve when that valve wasbeing moved from its closed to its open position, the delicate surfaceof the seat would be marred by the particles of the charge therebydestroying the gastight sealing fit between the same and the ball 25.The action of the charge restraining valve 21, however, permits freemovement of the vacuum closure valve without interference from orcontact with the particles of the charge. The butterfly valve 21 is thenmoved to its open position thereby permitting the batch of titaniumsponge or similar material 51 to fall by gravity into the lower hopper18 from where it feeds gradually through the open end 28 on to the feedtrough 34. The pulsating magnet assembly 38 is then energized therebysetting up a mag netic field of automatically reversing polarity in thewinding 39 and causing core 41 and with it shaft 36 to pulsate therebydelivering reciprocating motion to the trough 34 which will result in agradual delivery of the incremental batch of charge to the furnace asindicated at 52, with the actual rate of feed to the furnace dependingon the rate of reciprocation of the feed trough.

As soon as all of the first batch of charge 51 has emptied from theupper hopper It) the valves 21 and 23 will again be returned to theirclosed positions as shown in Fig. 2. The valve 16 of vacuum line is thenclosed and inert gas line valve 14 moved to its open position. Inertgas, such as argon, is then flooded into the hopper 10 until the samereturns to approximate atmospheric pressure as indicated on gauge 50. Atthis point, since the pressures above and beneath lid 11 areapproximately equalized, the lid may be opened and the secondincremental batch of charge introduced to the hopper 10. When thefurnace operator is convinced that the first charge has completelyemptied from the lower hopper 18, the above procedure is then repeatedthereby permitting the second batch to drop from the upper hopper 10 tothe lower hopper and then into the furnace via feed trough 34 in themanner described aforesaid.

This procedure is repeated over and over until all of the incrementalbatches of the charge have been introduced into the furnace at whichtime the ingot will have been produced having the desired overallchemical analysis 6 and moreover a substantially homogeneous structurethroughout.

Although certain particular embodiments of the invention are hereindisclosed for purposes of explanation, various further modificationsthereof, after study of this specification, will be apparent to thoseskilled in the art to which the invention pertains. Reference shouldaccordingly be had to the appended claims in determining the scope ofthe invention.

What is claimed and desired to be secured by Letters Patent. is:

1. Apparatus for feeding incremental batches of charge of highlyreactive metals and their alloying ingredients to a melting furnace,comprising a substantially gas-tight feed system having upper and lowerfeed receiving means interconnected by a feed conduit, vacuum closuremeans located in said feed conduit and adapted to seal off the upperfeed receiving means, when desired, from the rest of the feed system andcharge restraining valve means positioned in said conduit between thevacuum closure means and the upper feed receiving means and adapted,when closed, to prevent particles of the charge from contacting saidvacuum closure means, means connecting said lower feed receiving meansin open communication with the furnace, reciprocating feed deliverymeans positioned within said connecting means and adapted to receiveparticles of the batches of charge from the lower feed receiving meansand deliver them to the furnace, and activating means located exteriorlyof said gas-tight system and comprising a pulsating shaft extendingthrough a gas-tight seal into said feed system and being connected toone end of the feed receiving means for imparting reciprocating movementthereto.

2. Apparatus for feeding batches of charge of highly reactive metals andtheir alloying ingredients to a melting furnace comprising substantiallygas-tight upper and lower hoppers, a substantially gas-tight feed lineinterconnecting said hoppers, said feed line having a charge restrainingvalve and a vacuum closure valve positioned therein, a substantiallygas-tight enclosure providing open communication between the lowerhopper and the furnace, reciprocating feed means mounted in saidenclosure beneath said lowerhopper and adapted to receive the chargefrom said lower hopper and deliver the same to the furnace, means foractivating said feed means, said activating means being locatedexteriorly of the gas-tight enclosure and having a pulsating shaftextending in gas-tight sealing relationship into said enclosure andbeing operatively connected to the feed means.

3. Apparatus for feeding batches of charge of highly reactive metals andtheir alloying ingredients to a melting furnace comprising asubstantially gas-tight feed system, having upper and lower feedreceiving hoppers interconnected by a feed conduit and an enclosureconnecting the lower hopper with the furnace, a reciprocating feedtrough mounted in said enclosure of the feed system and adapted toreceive the charge from said lower hopper and convey it to the furnace,and an activating magnet assembly positioned externally of said feedsystem and having a pulsating shaft extending through a gas-tight sealinto the enclosure of said system, said shaft being connected to thefeed trough for imparting reciprocatory movement thereto.

4. Apparatus for feeding batches of charge of highly reactive metals andtheir alloying ingredients to a melting furnace comprising asubstantially gas-tight feed system, having upper and lower feedreceiving hoppers interconnected by a feed conduit, a vacuum closurevalve positioned in said feed conduit and a charge restraining valvepositioned in said conduit between the vacuum closure valve and theupper hopper, and an enclosure connecting the lower hopper with thefurnace, a reciprocating feed trough mounted in said enclosure of thefeed system and adapted to receive the charge from said lower hopper andconvey it to the furnace, and an activating magnet assembly positionedexternally of said feed system and having a pulsating shaft extendingthrough a gas-tight seal into the enclosure of said system, said shaftbeing-connected to one end of the feed trough for impartingreciproca'tor' 'mover'nentthe'reto.

5. A method of feeding a charge of particles of highly reactive metal,such as titanium sponge, and its alloying ingredients, said charge beingcharacterized by the varying gravimetric densities of the individualingredients thereof, in the desired proportions to a melting furnace soas to produce an ingot having the desired overall chemical analysis andhaving a substantially homogeneous structure throughout, which comprisesindividually weighing and blending according to the proportions desireda plurality of incremental batches of charge which together add up tothe overall charge desired, delivering the first of said batches to afeed receiving means of a vacuumtight feed system Whilemaintaining saidfeed receiving means sealed off from the remainder of said feed system,pumping down said remainder of the feed system to the desired furnaceoperating pressure, then sealing ofi said hopper from the atmosphere,pumping said hopper down to the desired operating pressure, then openingsaid hopper into communication with the remainder of said feed system,then delivering said first batch of charge to the furnace then closingoff said hopper from the remainder of the feed system and delivering thenext batch of charge thereto so as to commence the cycle all over again.

6. A method of feeding a charge of particles of highly reactive metalsto a furnace which comprises delivering a preweighed incremental batchof said charge to an upper feed receiving means of a substantiallygas-tight feed system while maintaining that upper feed receiving meanssealed oif from the remainder of said feed system, sealing off saidupper feed receiving means from the atmosphere, pumping down said feedreceiving means to a pressure corresponding to the operating pressure ofthe remainder of the feed system, then opening the feed receiving meansinto communication with the remainder of the system so as to deliver thefirst batch of charge to the furnace-and then sealing of? said-feedreceiving means from the remainder of the furnace so as to permitintrosmasher thenext batch of charge into thisfeedreceiving meanswithouteXposi-ngthe remaindenof the feed system to the atmosphere. i

7. A charge feeding system for'a furnace of the type wherein melting is'carried out under vacuum conditions comprising a substantially gas-tightfeed system having upper and lower feed hoppers interconnected by a feedline and nieans'interconnecting said lower hopper with the furnace,vacuum c-losure means provided insaid feed conduit whereby said upperhopper can be sealed oil from the remainder of said feed system andcharge restrainingmeans also located in said feed conduit betweenthevacuum closure means and the upper hopper and adapted when in theclosed'posit-ion to prevent particles of the charges from passing fromthe upper hopper into contact with the vacuum closure means, andreciprocating feed means positioned in' said feed system beneath thelower hopper thereof and adapted to receive the charge particles fromsaid lower hopper arid deliver the same to the furnace.

8. Apparatus for feeding batches of charge of highly reactive metalsand'their alloying ingredients to a melting furnace comprising asubstantially gas-tight feed system, having feed. receiving means andanenclosure connecting said feed receiving means with the furnace,vibratory charge feeding means mounted in said enclosure and adapted toreceive the charge from the feed receiving means and convey it to thefurnace, and an activating magnet assembly positioned'externally of saidfeed system and having .a' pulsating shaft extending into the feedsystem through a gas-tight .seal providedin a wall of the enclosure ofsaid-system,-.said shaft being connected to the feed trough forimparting reciprocatory movement thereto.

No references cited.

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